In the construction industry, heavy rolling equipment has advantageously used flat-proof, solid rubber, low profile tires on constructed to avoid slippage on metal wheel rims.
This construction advantageously avoided difficulties with punctured pneumatic tires or "flats" and also avoided the excessive weight and increased wear and breakdown of standard pneumatic tires filled with fluid rubber, elastomeric or urethane form material, which solidified in the tires to avoid flats. Downtime was reduced and cost-effective, economic usage in many applications for heavy equipment previously dominated with pneumatic tires proved such tires highly reliable and important in the industry. Particularly, for example, underground mining applications where downtime for changing pneumatic tires is extremely expensive, such rubber tires have become very important. Junkyard or metal yards or scrap metal facilities where puncturing of pneumatic tires is of prime concern, such solid rubber tires for large construction equipment have become important industry components.
Innovations in the area of wheel and solid rubber tire technology have been demonstrated in U.S. Pat. No. 4,966,212, issued to Giles Hill, Oct. 30, 1990 for a wheel and tire assembly with a solid rubber tire for use on heavy construction equipment. The assembly included a mounting disk, a large diameter rim having a circular surface rigidly affixed to the mounting disk, and having axially-opposed peripheral sides. Cross-ribs were rigidly fastened to the cylindrical surface of the rim across the cylindrical rim surface. Metal side support rims were rigidly affixed to and radially projecting from the peripheral side of the cylindrical rim surface. A base layer of even thickness of substantially flat rubber was submitted to the cylindrical surface, interposed between the cross-ribs and the side support rims. Multiple additional layers of even thickness of substantially flat sheet rubber were bonded to the base layer, and each succeeding additional layer was bonded to the preceding additional layer until a low profile, solid rubber tire was obtained. The solid rubber tire was thus bonded directly to the large diameter wheel rim for use on heavy construction equipment.
An improved method of constructing a wheel and low profile solid rubber tire was disclosed in U.S. Pat. No. 5,053,095, issued to Giles Hill, Oct. 1, 1991, for an improved method of constructing a wheel and tire assembly with a solid rubber tire for use on heavy construction equipment. The method included a mounting disk, a large diameter rim having a cylindrical surface and axially-opposed peripheral sides attached to the mounting rim. Cross ribs were rigidly fastened to and laterally across a cylindrical surface. There were side supporting rims rigidly affixed and radially projecting from the peripheral side of the cylindrical rim surfaces. A base layer of even thickness of substantially flat rubber was cemented to the cylindrical surface interposed between the cross rib and the side support rims. Multiple additional layers of even thickness substantially flat rubber were bonded to the base layer and each succeeding layer of even thickness was bonded to the preceding additional layer.
In both U.S. Pat. Nos. 4,966,212 and 5,053,095, it was contemplated that an interior core of a plurality of layers sequentially bonded rubber could include a softer rubber material surrounded on both sides by harder rubber sidewalls. The soft rubber core was designed to increase the flexibility of the solid rubber tire. However, in practice the increase in flexibility and cushioning of the ride due to the solid rubber core was significantly offset by the increased cost of producing sequential layers having side portions of one hardness rubber and a central portion of softer rubber. For this reason, such soft core solid rubber tires have not yet gained wide acceptance in the marketplace.
Previous attempts to smooth the ride have included putting air pockets or holes in the rubber below the wear layer or the tread layer thereby reducing the amount of rubber absorbing the impact between the outer wear layer and the rim. These attempts have provided some cushioning and have met with some success relative to other solid rubber tires. However, as the tread wears down there can be uneven support for the wear layer depending upon whether there is an air pocket or a web or spoke of rubber extended between the rim and the wear layer. This can lead to ripples developing in the tire when the tread wears thin.